The present invention relates to the field of friction clutches, and more specifically, to friction clutches having torsional vibration dampers.
Torsional vibrations are the rotational irregularities of a rotatingly driven component. In a vehicle drivetrain, torsional vibrations are caused by the forces generated within a combustion engine by the combustion of gases during the periodic combustion process. Torsional vibrations of the second or third order which originate from the engine, as a result of the ignition frequency of four or six cylinder engines, respectively, are predominant in the vehicle driveline. Torsional vibrations not only emanate from the engine power pulses but also from torque spikes and from abrupt changes in driveline torque due to rapid engine acceleration and deceleration.
Torsional vibrations cause premature wear to driveline components as well as audible noise. In a conventional driveline, the flywheel, which is rigidly connected to the crankshaft, will generate high reaction forces on the crankshaft. Torque irregularities from a periodic combustion also engine adds additional stress in the form of high frequency torques to the transmission. Furthermore, when a manual transmission is in neutral, gear rattle occurs, which is also an audible event, due to the teeth of meshing gears lifting away from another and then striking each other as a result of high frequency torque fluctuations.
Along with gear rattle, order based responses from the second or third engine order may be passed through the drivetrain and into the body structure. This sound can be greatly amplified if the components forming the sound are excited at their resonant frequencies.
Torsional vibration issues are further compounded by efforts to improve vehicle efficiency. Reductions in vehicle size and weight as well as reductions in driveline component inertia, such as flywheel masses, as well as reductions in transmission oil viscosity have added to the existing torsional vibration challenges. Lower drivetrain inertia results in a higher natural frequency of the drivetrain. As the engine rotational speed passes through the drivetrain natural frequency, resonant frequency occurs. The input displacement of a system is amplified at resonant frequency.
It is well known in the art to incorporate torsional vibration damping mechanisms in a dry clutch. As rotation occurs, the energy storage means within the damper, typically coil springs, provide the rotational compliance between the rotating elements. Another component of the damper is hysteresis, which is provided by friction producing elements. The hysteresis cooperates with the energy storage component of the damper to remove energy from the system.
The prior art is replete with friction clutches with dampers for attenuating torsional vibrations. A variety of spring arrangements have been employed to provide frictional force for damping. Most frictional dampers employ a diagram spring in some form to provide force along the axis of rotation of the clutch disk. In order to reduce weight for fuel economy and size for packaging purposes drivetrain components are being optimized. One way to meet size and weight requirements is to provide multipurpose parts in component assemblies. Many clutches employ a damper having a separate frictional spring element to provide force along the axis of rotation of the clutch disk to increase the hysteresis. A lighter and more compact clutch damper may be available by eliminating the need for a separate frictional spring element.
Therefore, there is a need in the art to provide an improved damper for a friction clutch which is lighter and more compact than a conventional friction clutch damper.
A friction clutch comprises a driving member having an axis of rotation, a cover coupled to the driving member for rotation therewith, a pressure plate coupled to the cover for rotation therewith and a driven disk coupled to an axially extending driven shaft for rotation therewith. The driven disk is interposed between the driving member and the pressure plate, the driven disk includes a rotatable disk assembly. The rotatable disk assembly includes a disk plate which rotates about an axis of rotation. The disk plate has a plurality of apertures and a plurality of friction pads attached thereto. A hub assembly which includes a hub secured to at least one spring cover plate having a plurality of apertures rotates relative to the disk assembly. The apertures in the disk assembly and the hub assembly are at least partially aligned. Energy storage means are disposed within the apertures in the disk assembly and hub assembly for absorbing torque as a function of relative rotation between the hub assembly and disk assembly. At least one reinforcing plate is disposed between the disk assembly and the hub assembly. The reinforcing plate has a plurality of undulations providing a load between the disk assembly and hub assembly.
In an alternate embodiment, the reinforcing plate may be coupled to the hub assembly or the disk assembly. Furthermore, the undulations in the reinforcing plate may be continuous. Also, the undulations may be disposed about an outer circumference of the reinforcing plate. The reinforcing plate may have a plurality of apertures disposed therein which are at least partially aligned with the apertures disposed in the disk assembly and the hub assembly.
The friction torque device may include a first reinforcing plate and a second reinforcing plate coupled to the hub assembly, where the disk plate of the disk assembly is disposed between the first and second reinforcing plates, each of the first and second reinforcing plates have a plurality of apertures that are at least partially aligned with the apertures disposed within the disk assembly and the hub assembly.
The driven disk of the friction torque device may further include a first spring cover plate and second spring cover plate coupled to the hub assembly where each of the first spring cover plate and second spring cover plate have a plurality of apertures that are at least partially aligned with the apertures disposed with one or more reinforcing plates and the disk plate.
Further objects, features and advantages of the present invention will become apparent to those skilled in the art from analysis of the following written description, the accompanying drawings and appended claims.